METHOD FOR PREPARING HYDROGEN-RICH SYNTHESIS GAS BY DEGRADING POLYOLEFIN WASTE PLASTICS AT LOW TEMPERATURE

Abstract

A method for preparing hydrogen-rich synthesis gas by degrading waste polyolefin plastics at a low temperature includes the following steps: weighing 1 part by weight of polyolefin waste plastics and 3 parts-80 parts by weight of hydrogen peroxide containing 0.25%-6% of H.sub.2O.sub.2; feeding the polyolefin waste plastics and the hydrogen peroxide into a hydrothermal reactor, and carrying out the oxidation pretreatment reaction at a reaction temperature of 150° C.-230° C. under a reaction pressure of 0.5 MPa-2 MPa for 30 minutes-90 minutes, and obtaining an aqueous-phase product and a gas-phase product after the reaction is finished; filling another hydrothermal reactor with a mesoporous carbon supported metal-based catalyst, and then introducing the aqueous-phase product into the hydrothermal reactor for a reforming reaction to obtain a hydrogen-rich synthesis gas product. In the whole process, the H.sub.2 yield is close to 11 mol/kg plastics, and the H.sub.2 concentration in the hydrogen-rich synthesis gas is close to 55%.

Claims

1. A method for preparing a hydrogen-rich synthesis gas by degrading polyolefin waste plastics at a low temperature, comprising the following steps: (1) weighing 1 part by weight of the polyolefin waste plastics and more than 3 parts by weight of hydrogen peroxide, wherein a concentration of H.sub.2O.sub.2 in the hydrogen peroxide is 0.25%-6%; (2) feeding the polyolefin waste plastics and the hydrogen peroxide into a first hydrothermal reactor, and carrying out an oxidation pretreatment reaction at a reaction temperature of 150° C.-230° C., and obtaining an aqueous-phase product and a gas-phase product after the oxidation pretreatment reaction is finished; (3) filling a second hydrothermal reactor with a mesoporous carbon supported metal-based catalyst, and then introducing the aqueous-phase product obtained in the step (2) into the second hydrothermal reactor for a reforming reaction to obtain a hydrogen-rich synthesis gas product.

2. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein a content of the H.sub.2O.sub.2 in the hydrogen peroxide in the step (1) is 0.5%-2%.

3. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein a weight of the hydrogen peroxide in the step (1) is 3 parts-80 parts by weight.

4. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 3, wherein the weight of the hydrogen peroxide in the step (1) is 5 parts-10 parts by weight, a reaction pressure in the step (2) is 0.5 MPa-2 MPa, and a reaction time is 30 min-90 min.

5. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 4, wherein in the step (2), the reaction temperature is 190° C.-200° C., the reaction pressure is 1 MPa, and the reaction time is 30 min-60 min.

6. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein a main component of the aqueous-phase product obtained in the step (2) is acetic acid, and the gas-phase product is oxygen and CO.sub.2.

7. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein a reaction temperature of the reforming reaction in the step (3) is 200° C.-240° C., a reaction pressure of the reforming reaction in the step (3) is 2 MPa-4 MPa, and a reaction time of the reforming reaction in the step (3) is 120 min-180 min.

8. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein the mesoporous carbon supported metal-based catalyst in the step (3) is one or more of a mesoporous carbon supported Ru monometal, a mesoporous carbon supported Ni monometal, a mesoporous carbon supported Pt monometal, and a mesoporous carbon supported Ru—Ni bimetal.

9. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 8, wherein the mesoporous carbon supported metal-based catalyst in the step (3) is a mesoporous carbon supported Ru—Ni bimetallic catalyst, and a mass ratio of Ru to Ni is 4:1, 1:1, or 1:4.

10. The method for preparing the hydrogen-rich synthesis gas by degrading the polyolefin waste plastics at the low temperature according to claim 1, wherein the polyolefin waste plastics are selected from one or more of polypropylene, a low-density polyethylene, and a high-density polyethylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a graph showing the change of the concentration of H.sub.2O.sub.2 and the yield of each product in the present application;

[0040] FIG. 2 is a graph of the concentration of H.sub.2O.sub.2 and the gas composition in the synthesis gas product of the present application;

[0041] FIG. 3 is a graph showing the relationship between the concentration of H.sub.2O.sub.2 and the selectivity of hydrogen in the present application;

[0042] FIG. 4 is a graph showing the relationship between the mass ratio of hydrogen peroxide to polyolefin and the yield of synthesis gas;

[0043] FIG. 5 is a graph showing the relationship between H.sub.2O.sub.2 concentration and CO.sub.2 produced by pre-oxidation treatment in the present application;

[0044] FIG. 6 is the nitrogen adsorption-desorption isotherm of the fresh catalyst synthesized by the present application;

[0045] FIG. 7 is a schematic diagram of pore size distribution of fresh catalyst synthesized by the present application;

[0046] FIG. 8 is an XRD schematic diagram of a fresh catalyst synthesized by the present application;

[0047] FIGS. 9A-9C are TEM images and particle size distribution diagrams of the mesoporous carbon supported catalyst of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

EXAMPLE 1

[0048] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 6% H.sub.2O.sub.2 hydrogen peroxide, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the H.sub.2O.sub.2-plastic ratio was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0049] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ru monometallic catalyst; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, and a reaction pressure of 4 MPa.

[0050] The preparation method of mesoporous carbon supported Ru monometallic catalyst comprised the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding a certain amount of mesoporous carbon and ruthenium chloride into deionized water, stirring and immersing at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated to dryness, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H.sub.2-90% Ar at 550° C. for 4 hours.

EXAMPLE 2

[0051] Step 1: Commercial 30% H.sub.2O.sub.2 hydrogen peroxide was diluted with deionized water to prepare 80 ml of 4% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0052] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 3

[0053] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 2% H.sub.2O.sub.2 hydrogen peroxide, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were load into a hydrothermal reactor so that the H.sub.2O.sub.2 to plastic ratio was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0054] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 4

[0055] Step 1: Commercial 30% H.sub.2O.sub.2 hydrogen peroxide was diluted with deionized water to prepare 80 ml of 1% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the H.sub.2O.sub.2 to plastic ratio was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0056] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 5

[0057] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0058] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 6

[0059] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.25% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0060] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 7

[0061] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 3:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0062] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 8

[0063] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 5:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and 02.

[0064] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 9

[0065] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 20:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0066] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 10

[0067] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 40:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0068] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 11

[0069] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 80:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0070] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 12

[0071] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 180° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0072] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 13

[0073] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 190° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0074] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 14

[0075] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 210° C., a reaction time of 60 min, reaction pressure 2 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0076] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 15

[0077] Step 1 was the same as step 1 of Example 1.

[0078] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ni monometal catalyst; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, and a reaction pressure of 4 MPa.

[0079] The preparation method of the mesoporous carbon supported Ni monometal catalyst included the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding adding a certain amount of mesoporous carbon and nickel chloride hexahydrate added into deionized water, stirring and immersing at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated to dryness, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H2-90% Ar at 550° C. for 4 hours.

EXAMPLE 16

[0080] Step 1 was the same as step 1 of Example 1.

[0081] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Pt monometallic catalyst; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, and a reaction pressure of 4 MPa.

[0082] The preparation method of the mesoporous carbon supported Pt monometallic catalyst included the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding adding a certain amount of mesoporous carbon and chloroplatinic acid into deionized water, stirring and immersing at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated to dryness, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H2-90% Ar at 550° C. for 4 hours.

EXAMPLE 17

[0083] Step 1 was the same as step 1 of Example 1.

[0084] Step 2, the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ru—Ni bimetallic catalyst, wherein the mass ratio of Ru to Ni in the mesoporous carbon supported Ru—Ni bimetallic catalyst was 4:1; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

[0085] The preparation method of the Ru—Ni bimetallic catalyst supported by mesoporous carbon included the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding a certain amount of mesoporous carbon, nickel chloride hexahydrate and ruthenium chloride into deionized water in proportion, stirred and immersed at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H2-90% Ar at 550° C. for 4 hours.

EXAMPLE 18

[0086] Step 1 was the same as step 1 of Example 1.

[0087] Step 2, the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ru—Ni bimetallic catalyst, wherein the mass ratio of Ru to Ni in the mesoporous carbon supported Ru—Ni bimetallic catalyst was 1:1; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

[0088] The preparation method of the Ru—Ni bimetallic catalyst supported by mesoporous carbon included the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding a certain amount of mesoporous carbon, nickel chloride hexahydrate and ruthenium chloride into deionized water in proportion, stirred and immersed at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H.sub.2-90% Ar at 550° C. for 4 hours.

EXAMPLE 19

[0089] Step 1 was the same as step 1 of Example 1.

[0090] Step 2, the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ru—Ni bimetallic catalyst, wherein the mass ratio of Ru to Ni in the mesoporous carbon supported Ru—Ni bimetallic catalyst was 1:4; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

[0091] The preparation method of the Ru—Ni bimetallic catalyst supported by mesoporous carbon included the following steps: sieving mesoporous carbon to 120-150 meshes; according to the total metal loading of 5 wt %, adding a certain amount of mesoporous carbon, nickel chloride hexahydrate and ruthenium chloride into deionized water in proportion, stirred and immersed at room temperature for 12 hours, then continuing to stir at 80° C. until the water was evaporated, and drying the obtained sample in an oven at 105° C. for 12 hours; reducing in 10% H.sub.2-90% Ar at 550° C. for 4 hours.

EXAMPLE 20

[0092] Step 1 was the same as step 1 of Example 1.

[0093] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru—Ni bimetallic catalyst, wherein the mesoporous carbon-loaded Ru—Ni bimetallic catalyst was the mesoporous carbon-loaded Ru—Ni bimetallic catalyst recovered in Example 17; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 21

[0094] Step 1 was the same as step 1 of Example 1.

[0095] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru—Ni bimetallic catalyst, wherein the mesoporous carbon-loaded Ru—Ni bimetallic catalyst was the mesoporous carbon-loaded Ru—Ni bimetallic catalyst recovered in Example 20; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 22

[0096] Step 1 was the same as step 1 of Example 1.

[0097] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru—Ni bimetallic catalyst, wherein the mesoporous carbon-loaded Ru—Ni bimetallic catalyst was the mesoporous carbon-loaded Ru—Ni bimetallic catalyst recovered in Example 21; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 23

[0098] Step 1 was the same as step 1 of Example 1.

[0099] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru monometallic catalyst, wherein the Ru monometallic catalyst was the Ru monometallic catalyst recovered in Example 5; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 24

[0100] Step 1 was the same as step 1 of Example 1.

[0101] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru—Ni bimetallic catalyst, wherein the mesoporous carbon-loaded Ru—Ni bimetallic catalyst was the mesoporous carbon-loaded Ru—Ni bimetallic catalyst recovered in Example 23; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 25

[0102] Step 1 was the same as step 1 of Example 1.

[0103] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with mesoporous carbon-loaded Ru—Ni bimetallic catalyst, wherein the mesoporous carbon-loaded Ru—Ni bimetallic catalyst was the mesoporous carbon-loaded Ru—Ni bimetallic catalyst recovered in Example 24; the reaction conditions were: a reaction temperature of 240° C., a reaction time of 120 min, a reaction pressure of 4 MPa.

EXAMPLE 26

[0104] Step 1: commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of high density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor, so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0105] Step 2 was the same as step 2 of Example 17; the catalyst was prepared in the same way as in Example 17.

EXAMPLE 27

[0106] Step 1: commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 2% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g polypropylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0107] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 28

[0108] Step 1: commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 1% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g polypropylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., a reaction time of 60 min, a reaction pressure of 0.5 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0109] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 29

[0110] Step 1: commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of high density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor, so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., reaction time 30 min, reaction pressure 1 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0111] Step 2: the aqueous-phase product of the first stage of oxidation pretreatment was introduced into a reactor filled with a mesoporous carbon supported Ru—Ni bimetallic catalyst, wherein the mass ratio of Ru to Ni in the mesoporous carbon supported Ru—Ni bimetallic catalyst was 4:1; the reaction conditions were: a reaction temperature of 200° C., reaction time 180 min and reaction pressure 2 MPa.

[0112] The catalyst was prepared in the same way as in Example 16.

EXAMPLE 30

[0113] Step 1: commercial 30% H.sub.2O.sub.2 hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 hydrogen peroxide solution, and 0.16 g of high density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor, so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 200° C., reaction time 90 min, reaction pressure 1 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0114] Step 2 was the same as step 2 of Example 29; the catalyst was prepared in the same way as in Example 17.

EXAMPLE 31

[0115] Step 1: commercial 30% H.sub.2O.sub.2 hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 150° C., a reaction time of 60 min, reaction pressure 2 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0116] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 32

[0117] Step 1: commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 220° C., a reaction time of 60 min, reaction pressure 2 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0118] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

EXAMPLE 33

[0119] Step 1: Commercial 30% H.sub.2O.sub.2 of hydrogen peroxide solution was diluted with deionized water to prepare 80 ml of 0.5% H.sub.2O.sub.2 of hydrogen peroxide solution, and 0.16 g of low density polyethylene and the prepared dilute hydrogen peroxide solution were loaded into a hydrothermal reactor so that the ratio of H.sub.2O.sub.2 to plastic was 10:1; the reaction conditions were: a reaction temperature of 230° C., a reaction time of 60 min, reaction pressure 2 MPa; the main aqueous-phase product obtained by the pretreatment was acetic acid, and the gas-phase products were CO.sub.2 and O.sub.2.

[0120] Step 2 was the same as step 2 of Example 1; the catalyst was prepared in the same way as in Example 1.

[0121] The gas-phase products obtained from the catalytic reforming of Examples 1-33 were tested by gas chromatography, and the related indexes were calculated. The experimental data are shown in Table 1:

TABLE-US-00001 TABLE 1 Pretreatment Pretreatment H.sub.2O.sub.2 H.sub.2O.sub.2- Reforming H.sub.2 yield H.sub.2 temperature time concent plastic temperature Mol/kg concentration Example (° C.) (min) ration ratio (° C.) Reforming catalyst plastic (%) one 200 60 six 10:1 240 Ru/MEC 3.07 41.7 2 200 60 four 10:1 240 Ru/MEC 3.41 44.3 three 200 60 2 10:1 240 Ru/MEC 4.52 49.1 four 200 60 one 10:1 240 Ru/MEC 7.35 48.6 five 200 60 0.5 10:1 240 Ru/MEC 10.83 51.5 six 200 60 0.25 10:1 240 Ru/MEC 10.34 49.2 seven 200 60 0.5  3:1 240 Ru/MEC 2.3 51.1 eight 200 60 0.5  5:1 240 Ru/MEC 4.7 53.6 nine 200 60 0.5 20:1 240 Ru/MEC 13.1 45.3 10 200 60 0.5 40:1 240 Ru/MEC 15.2 44.7 11 200 60 0.5 80:1 240 Ru/MEC 15.3 42.1 12 180 60 0.5 10:1 240 Ru/MEC 5.29 47.2 13 190 60 0.5 10:1 240 Ru/MEC 8.22 48.9 14 210 60 0.5 10:1 240 Ru/MEC 9.92 50.6 15 200 60 0.5 10:1 240 Ni/MEC 2.89 27.1 16 200 60 0.5 10:1 240 Pt/MEC 5.06 32.2 17 200 60 0.5 10:1 240 4Ru-1Ni/MEC 9.58 45.1 18 200 60 0.5 10:1 240 1Ru-1Ni/MEC 5.54 45 19 200 60 0.5 10:1 240 1Ru-4Ni/MEC 4.37 34 20 200 60 0.5 10:1 240 4Ru-1Ni/MEC recovered 7.29 49.1 in Example 17 21 200 60 0.5 10:1 240 4Ru-1Ni/MEC recovered 7.43 49.1 in Example 20 22 200 60 0.5 10:1 240 4Ru-1Ni/MEC recovered 7.4 49.1 in Example 21 23 200 60 0.5 10:1 240 Ru/MEC recovered in 7.34 49.1 Example 5 24 200 60 0.5 10:1 240 Ru/MEC recovered in 7.25 49.1 Example 23 25 200 60 0.5 10:1 240 Ru/MEC recovered in 6.77 49.1 Example 24 26 200 60 0.5 10:1 240 4Ru-1Ni/MEC 8.61 42.7 27 200 60 2 10:1 240 Ru/MEC 6.5 48 28 200 60 one 10:1 240 Ru/MEC 7.2 46 29 200 30 0.5 10:1 200 4Ru-1Ni/MEC 8.8 36.7 30 200 90 0.5 10:1 240 4Ru-1Ni/MEC 9.41 52.5 31 150 60 0.5 10:1 240 Ru/MEC 3.35 43.4 32 220 60 0.5 10:1 240 Ru/MEC 10.30 51.13 33 230 60 0.5 10:1 240 Ru/MEC 8.61 51.26 Note: MEC is mesoporous carbon; Ru/MEC is a mesoporous carbon supported Ru monometal catalyst; Ni/MEC is a mesoporous carbon supported Ni monometal catalyst; Pt/MEC is a mesoporous carbon supported Pt monometal catalyst; Ru-1Ni/MEC is a mesoporous carbon supported Ru-Ni bimetallic catalyst, and the mass ratio of Ru to Ni is 4:1. Ru-1Ni/MEC is a mesoporous carbon supported Ru-Ni bimetallic catalyst, and the mass ratio of Ru to Ni is 1:1. Ru-4Ni/MEC is a mesoporous carbon supported Ru-Ni bimetallic catalyst, and the mass ratio of Ru to Ni is 1:4. The ratio of H.sub.2O.sub.2 to plastic was the mass ratio of hydrogen peroxide to polyolefin.

[0122] It can be seen from Examples 1-6 that when the concentration of H.sub.2O.sub.2 in the first reaction is 0.25%-1%, the yield and concentration of hydrogen obtained in the second reaction is better, and when the concentration of H.sub.2O.sub.2 is 0.5%, the hydrogen production effect is the best.

[0123] According to Examples 1-6, the relationship between the concentration of H.sub.2O.sub.2 and the yield of each product was studied. The results are shown in FIG. 1. In the figure, the abscissa indicates the concentration of H.sub.2O.sub.2 in wt %, and the ordinate indicates the yield of each product in mol/kg. In the figure, C.sub.1-C.sub.3 indicates C.sub.1-C.sub.3 alkane olefin, CO indicates carbon monoxide, CO.sub.2 indicates CO.sub.2, and H.sub.2 indicates hydrogen. It can be seen from FIG. 1 that as the concentration of H.sub.2O.sub.2 decreases from 8% (H.sub.2 yield was 3.05 mol/kg) to 0.5% (H.sub.2 yield was 10.83 mol/kg), the H.sub.2 yield shows an obvious increasing trend. However, when the concentration of H.sub.2O.sub.2 was further reduced to 0.25%, the H.sub.2 production decreased from 10.83 mol/kg to 10.34 mol/kg, which decreased by 4.5%, which was due to the insufficient oxidation caused by the low concentration of H.sub.2O.sub.2. When the concentration of H.sub.2O.sub.2 is 0.25%, the output of CO.sub.2 is 3.65 mol/kg. This is because CO.sub.2 is not only produced by the peroxidation of carboxylic acid, but also directly formed during the oxidative cracking of C—C bond during the oxidative pretreatment. The high concentration CO.sub.2 produced in the pretreatment process may be used for further carbon capture, utilization and storage.

[0124] According to Examples 1-6, the relationship between the concentration of H.sub.2O.sub.2 and the composition of gas components in the synthesis gas product was studied. The results are shown in FIG. 2. In the figure, the abscissa indicates the molar fraction of each gas component, and the ordinate indicates the concentration of H.sub.2O.sub.2 in wt %. For the reforming reaction, the molar fraction of H.sub.2 in the product synthesis gas is more than 40%, and it reaches the maximum value (51.52%) when the concentration of H.sub.2O.sub.2 is 0.5% under all H.sub.2O.sub.2 concentrations.

[0125] H.sub.2O.sub.2, as a strong oxidant, will over-oxidize the raw materials at a high concentration (6%-8%), leading to oxidative cracking of C—C bonds, resulting in a higher by-product CO.sub.2 yield. Lowering the concentration of H.sub.2O.sub.2 will significantly reduce the CO.sub.2 yield, which can effectively weaken the peroxidation of carboxylic acids produced in the pre-oxidation stage, thus ensuring that more carboxylic acids will participate in the reaction in the second hydrogen production process and promoting the production of hydrogen.

[0126] The relationship between H.sub.2O.sub.2 concentration and hydrogen selectivity was studied according to Examples 1-6, and the results are shown in FIG. 3. In the figure, the abscissa indicates the concentration of H.sub.2O.sub.2 in wt %, and the ordinate indicates the mole fraction of CO.sub.2 in synthesis gas and hydrogen selectivity; It can be seen from FIG. 3 that during the reforming reaction, with the decrease of H.sub.2O.sub.2 concentration, the conversion of carbon to CO.sub.2 increases.

[0127] According to Example 5 and Examples 7-11, the effect of hydrogen peroxide-polyolefin ratio on synthesis gas yield was studied, and the results are shown in FIG. 4. In the figure, the abscissa indicates the mass ratio of hydrogen peroxide-polyolefin, and the ordinate indicates the synthesis gas yield and the mole fraction of hydrogen and CO.sub.2 in synthesis gas. It can be seen from FIG. 4 that when the mass ratio of hydrogen peroxide to polyolefin is 10:1, the concentration of hydrogen in the synthesis gas obtained in the second stage process and the yield of synthesis gas are the best.

[0128] According to Examples 1-6, the effect of H.sub.2O.sub.2 concentration on CO.sub.2 produced by pre-oxidation treatment was studied, and the results are shown in FIG. 5. In the figure, the left abscissa indicates the concentration of H.sub.2O.sub.2 in wt %, the right abscissa indicates the mass ratio of hydrogen peroxide to polyolefin, and the ordinate indicates the output of CO.sub.2 in mol/kg. It can be seen from FIG. 5 that the amount of CO.sub.2 produced in the oxidation pretreatment process increases with the decrease of the amount of plastic. This may be due to the fact that during the cleavage of C—C bond, more H.sub.2O.sub.2 promotes the production of CO.sub.2, rather than over oxidation. However, when the mass ratio of hydrogen peroxide to polyolefin is higher, the reforming process produces more CO.sub.2, which leads to the decrease of the molar fraction of H.sub.2 in the gas product.

[0129] To sum up, it can be concluded that when the concentration of H.sub.2O.sub.2 in the first reaction is 0.25%-1%, the yield and concentration of hydrogen in the second reaction is better, and when the concentration of H.sub.2O.sub.2 is 0.5%, the hydrogen production effect is the best.

[0130] According to Example 5 and Examples 12-14, when the pretreatment temperature in the first stage is 200° C., the H.sub.2 yield and concentration in the synthesis gas obtained in the second stage are the highest.

[0131] According to examples 5 and 15-19, the order of the catalytic performance of mesoporous carbon supported Ru, Ni, Pt monometallic catalysts and Ru—Ni bimetallic catalyst in the second stage of the present application is Ru/MEC>4Ru-1Ni/MEC>1Ru-1Ni/MEC>Pt/MEC>1Ru-4Ni/MEC>Ni/MEC. The pore structures of the fresh catalysts in Example 5 and Examples 14-17 were characterized, and the results are shown in Table 2.

TABLE-US-00002 TABLE 2 Specific surface Pore volume Average pore Catalyst area (m.sup.2/g) (cm.sup.3/g) size (nm) MEC 1321.95 1.71 5.17 Ru/MEC 1211.57 1.42 4.7 4Ru—1Ni/MEC 1301.93 1.67 5.12 1Ru—1Ni/MEC 1288.99 1.63 5.07 1Ru—4Ni/MEC 1206.17 1.54 5.09 Ni/MEC 1203.87 1.58 5.23

[0132] The nitrogen adsorption-desorption isotherms of the fresh catalysts synthesized in Example 5 and Examples 15-19 are shown in FIG. 6. In FIG. 6, the abscissa indicates the relative pressure P/P.sup.0, where P.sup.0 indicates the saturated vapor pressure of the gas at the adsorption temperature, P indicates the pressure of the gas phase at the adsorption equilibrium, and the ordinate indicates the adsorption amount measured in the standard state (unit: cm.sup.3/g); the pore size distribution of the fresh catalyst was shown in FIG. 7, where the abscissa indicates the pore size (unit: nm) and the ordinate indicates the pore volume (cm.sup.3/g). It can be seen from FIG. 6 and FIG. 7 that all catalysts are type IV isotherms, with narrow pore size distribution and the center at about 5 nm. This is because these catalysts have a developed mesoporous structure, and these catalysts have a specific surface area of 1,000-1,400 m.sup.2/g. Compared with mesoporous carbon, the specific surface area and pore volume of all mesoporous carbon supported metal-based catalysts are lower, which is due to the introduction of metal particles in the pores of mesoporous carbon, resulting in the decrease of the specific surface area and pore volume. Compared with Ru/MEC, 4Ru-1Ni/MEC has higher specific surface area and pore volume, while 1Ru-1Ni/MEC and 1Ru-4Ni/MEC have lower specific surface area and pore volume. These results show that the addition of a small amount of the second metal improves the texture performance of the monometal catalyst.

[0133] The XRD spectra of Ni/MEC, Ru/MEC and bimetallic catalysts with different molar ratios are shown in FIG. 8. For Ni/MEC, there are big peaks at 44.5° and 51.5°, which correspond to the Ni (111) plane and the Ni (200) plane respectively. In the XRD spectra of Ru/MEC and Ru-based bimetallic catalysts, there are two weak peaks at 38.5° and 42.3°, respectively, which represent the 100 and 002 crystal planes of Ru species. The weak diffraction peaks of the metal Ru in Ru/MEC and Ru—Ni bimetallic catalysts show that Ru nanoparticles are small in size and highly dispersed on the surface of MEC, which is consistent with the scanning results of the electron microscope. Small nanoparticles can provide more surface atoms, thus improving their catalytic activity.

[0134] According to Example 5, Example 17 and Examples 20-25, the mesoporous carbon supported Ru—Ni bimetallic catalyst shows higher stability than Ru monometal under the operating conditions of the present application.

[0135] The TEM images and particle size distribution of single and bimetallic carbon supported catalysts are shown in FIGS. 9A-9C. FIG. 9A is the TEM and particle size distribution image of Ni/MEC, FIG. 9B is the TEM and particle size distribution image of Ru/MEC, and FIG. 9C is the TEM and particle size distribution image of 4Ru-1Ni/MEC. The average particle size of Ru—Ni is 14.1 nm, which is larger than that of monometal Ru/MEC (with an average particle size of 7.2 nm). This phenomenon may be due to the synergistic effect of Ru and Ni. After observation, Ru and Ni atoms are almost in the same position, and each atom is not separated in the whole imaging area, which indicates that a uniform Ru—Ni alloy structure is formed.

[0136] Further study the influence of the operating parameters of the oxidation pretreatment reaction on the performance of the oxidation pretreatment in the first stage and the reforming reaction in the second stage. The experimental results are shown in Table 3:

TABLE-US-00003 TABLE 3 Carbon is converted Oxidation into gas (%, Acetic pre- pre- Gas output (mol/kg) H.sub.2 CO.sub.2 acid treatment Temperature treatment + H.sub.2 (%, CO.sub.2- selectivity output output time (min) (° C.) reforming) reforming) H2 reforming C.sub.2-C.sub.3 (%) (mol/kg) (mol/kg) 60 180 12.83 47.23 5.29 6.12 0.037 85.94 2.93 1.48 60 190 18.56 48.97 8.22 8.87 0.058 92.16 4.22 1.68 60 200 21.68 51.52 10.84 8.36 0.108 127.92 6.88 2.00 60 210 25.13 50.62 9.92 9.99 0.070 98.57 7.74 1.86 60 220 28.76 51.13 10.30 10.17 0.074 100.61 10.13 1.85 60 230 27.31 51.26 8.61 8.44 0.065 101.22 10.84 1.93 30 200 16.32 50.58 7.93 8.01 0.050 98.35 3.5 1.82 60 200 21.68 51.52 10.84 8.36 0.108 127.92 6.88 2.00 90 200 22.88 52.53 9.41 8.78 0.063 106.45 7.37 1.86 120 200 27.70 51.63 9.83 9.51 0.066 102.62 10.04 1.80

[0137] It can be seen from Table 3 that the oxidation reaction of polyolefin is weakened at a lower hydrothermal temperature, and the decarboxylation reaction of organic compounds, that is, the thermal cracking of long-chain carboxylic acids, may occur in the hydrothermal environment above 220° C. Too long pre-oxidation reaction time will adversely affect the reforming reaction. When the time of oxidation pretreatment is 60 min and the temperature is 200° C., the yield of acetic acid is the highest, which is most beneficial to the subsequent reforming reaction.

[0138] The catalytic activity of fresh bimetallic 4Ru-1Ni/MEC catalyst was the most similar to that of monometal Ru catalyst, so 4Ru-1Ni/MEC catalyst and Ru/MEC catalyst were selected for stability test and comparison. After each use, the catalyst was recovered and dried overnight in an oven at 105° C. Compared with the first run, the H.sub.2 yield and H.sub.2 mole fraction in the second run decreased obviously, and the changes in the third and fourth runs were stable. The degradation of catalyst performance is due to the deactivation of catalyst caused by carbon deposition and active metal sintering.

[0139] The results of Examples 20-25 show that the specific surface areas of 4Ru-1Ni/MEC and Ru/MEC catalysts have decreased after use. Although the average pore size of the two catalysts has decreased after use, the pore size distribution of the catalysts is still narrow, and the center position is about 5 nm. In addition, no NiO peak was observed in the XRD spectrum of mesoporous carbon supported Ru—Ni bimetallic catalyst, which may be due to the inhibition of metal Ru on Ni oxidation. Compared with the second operation, the hydrogen production in the third and fourth operation has little change, but the molar fraction of H.sub.2 keeps decreasing. The H.sub.2 yield and H.sub.2 mole fraction in the mesoporous carbon supported Ru—Ni bimetallic catalyst reforming process are higher than those of mesoporous carbon supported Ru bimetallic catalyst. This shows that due to the interaction between two metals, Ru—Ni bimetallic catalyst has higher stability than monometal Ru catalyst.

[0140] The above embodiments are illustrative of the present application, but not restrictive, and any simple modification of the present application belongs to the scope of protection of the present application.